Document

• Growth and yield
• Harvesting
• Regeneration
• Thinning
• Fire and fuels
• Forested stands are the product of past disturbances and
management. Understanding how some disturbance (for
example, fire, harvest, etc.) history has influenced current stand
structure or how it changes and develops in the future (that is,
forest stand dynamics)
• For example, a silviculturist may want to evaluate different
management regimes to see how differentiation, the divergence
in growth patterns of individual trees, affects the stand structure
in terms of crown classes or how it might influence stand and
stock tables.
• dominant: trees whose crown extends above the general level of the
main canopy of even-aged stands, or in uneven-aged stands, above
the crowns of the tree's immediate neighbors and receiving full light
from above and partial light from the sides.
• codominant: a tree whose crown helps to form the general level of the
main canopy in even-aged stands, or in uneven-aged stands, the main
canopy of the tree's immediate neighbors, receiving full light from
above and comparatively little from the sides.
• intermediate: trees with crowns either below or extending into the
canopy formed by codominant and dominant trees; receiving little
direct light from above and none from the sides; usually with small
crowns considerably crowded on the sides.
• overtopped: trees with crowns entirely below the general level of the
crown cover receiving little or no direct light from above or from the
sides.
• Growth is the change in biomass,
size, volume, weight or other characteristic
of interest over a specified time period.
• Yield is the existing amount of that
characteristic of interest for a particular
type of forest stand by species, site,
stocking, and management regime at a
specified point in time.
• Growth example, let's say your stand of slash pine might
increase in volume by 2,000 cubic feet over 10 years. If we
state this as an annual increment, we would say that the stand's
growth is equal to 200 cubic feet per year (2,000 cubic feet
per year / 10 years).
• Yield actually has 2 meanings. It is:
• the amount of some characteristic that can be harvested per period, or
• the total amount that could be removed at any time
• Current (CAI) – the increment over a period of one
year at any stage in a tree’s life
• MAI = yield @ age A/Age A
• PAI = Yield @ age A2 – Yield @ age A1
-----------------------------------------age A2 – age A1
• PAI = sum of CAI from age A2 to A1
----------------------------------age A2 – age A1
•Age X MAI
•Sum of CAI from 0 to Age A
• A measure of the stocking of a stand
of trees based on the number of trees
per unit area and diameter at breast
height of the tree of average basal
area (QMD)
• log10SDI = log10N + 1.605 log10D - 1.605
• Example: Given BA = 150 sq ft and N = 400 trees per acre, the
QMD =
•
•
•
•
150
400 .005454
= 8.29
Thus
log10SDI = log10(400) + 1.605log10(8.29) - 1.605 = 2.47
SDI = 102.47
SDI = 295
• BA used instead since easier to calculate and well-correlated to SDI
• For pure even aged stands crowded to the point of self thinning
the mathematical relationship exists
• Log (mean tree volume) = -3/2 log (tree density) + C
• C is a constant that varies by species
• Mathematically equivalent to SDI
A – unit area (43560 ft2 or 10000 m2)
• RS = 43560//
• N = number of trees per acre
• H = average Height of the dominant canopy in feet
• Measure of stand density
• Independent of site quality, stand age, stand
structure (even or uneven-age stands)
• Definition: Area available to the average tree in a
stand compared to the maximum area used by an
open-grown tree with the same diameter
• Crown Width (CW) vs. DBH – linear relationship
• Maximum crown area (MCA): crown area of an
open-grown tree of diameter DBH, expressed as %
of unit area (1 ac or 1 ha)
• coppice method - the main regeneration method is vegetative
sprouting of either suckers (from the existing root system or cut trees)
or shoots (from cut stumps).
• even-aged methods - a regeneration method designed to regenerate
and maintain a stand with a single age class and includes:
• clearcutting - the cutting of essentially all trees, producing a fully exposed
microclimate for the development of a new age class.
• seed tree - an even-aged regeneration method in which selected trees (seed
trees) are left standing after the initial harvest to provide a seed source
for natural regeneration. Seed trees can be left uniformly distributed or in
small groups. Although regeneration is generally secured naturally, it may be
augmented by planting. Seed trees are often removed once regeneration is
established or may be left as reserves.
• shelterwood - a regeneration method in which trees are removed as a series
of cuts designed to achieve a new even-aged stand under the shelter of
remaining trees.
• two-aged methods - a regeneration method designed to
regenerate and maintain a stand with two age classes, usually
through the retention of reserve trees in the overstory.
• uneven-aged methods - (also known as selection methods) a
regeneration method designed to create or maintain and
regenerate an uneven-aged stand structure, including:
• single tree selection - a regeneration method in which individual trees of
all size classes are removed more or less uniformly throughout the stand to
promote growth of regeneration.
• group selection - a regeneration method which removes trees and
facilitates regeneration in small groups.
• thinning from below - (also known as ordinary, German, or low
thinning) the removal of trees from the lower crown classes to
favor those in the upper crown classes.
• thinning from above - (also known as French or crown thinning)
the removal of trees from the dominant or codominant crown
classes to favor the best trees of those same crown classes.
• selection thinning - the removal of trees from the upper crown
classes to favor trees in the lower crown classes.
• row thinning - (also known as mechanical or geometric thinning)
the removal of trees in rows, strips, or using fixed spacing
intervals.
• Timber managers may be interested in decreasing
wildland fire hazard. To do so, they need to
understand the fire types such as surface, passive and
active crown fires and their effects on stands. In
addition, managers may want to look at stand
attributes such as canopy bulk density and canopy base
height. This information can help predict fire types
and spread so they can be managed or prevented.
• Thinning reduces and redistributes fuel loads thus fire
hazards.